1. Field of the Invention
This invention relates to plasticized PVC compositions, and, more particularly, to stable plasticized PVC compositions including a C4-C30 alkyl pyrrolidone present in an amount sufficient to plasticize PVC and impart flexibility, softness, extensibility and lower melting temperatures to the PVC.
2. Description of the Prior Art
It is well known in the prior art that addition of certain organic compounds, called plasticizers, to PVC confers on the PVC desirable properties such as flexibility, softness, good feel and ease of processability, extensibility and lower melting temperature [Encyclopedia of PVC Vol. 1 and 2, L. I. Nass (1976)]. Plasticizers function by dissolving in PVC, reducing the cohesive energy density between the polymer chains and reducing the polar forces exerted by the halogen atoms present in PVC. For any organic compound to function as an effective plasticizer for PVC it (a) must possess very high miscibility with PVC, (b) must have polar groups and (c) must have a low tendency to diffuse and migrate out of the polymer during its effective service life. In addition, the plasticizer must not cause coloration to PVC, should be non-toxic, odorless, possess low volatility and be thermally stable at the temperature of mixing and compounding of PVC with the plasticizer.
A variety of organic compounds have been reported as effective plasticizers for PVC. These include esters of phthalic anhydride with aliphatic alcohols (linear/branched) with four to fifteen carbon atoms, epoxidized soybean oil, esters of trimellitic acids, phosphates, esters of benzoic and citric acids, and halogenated hydrocarbons. Higher molecular weight polyesters (800-6000) prepared by condensation of diols with adipic or sebacic acids are also used as plasticizers. Of these, phthalate-based plasticizers are the most widely used because of their excellent compatibility with PVC, ease of fusion and all-around desirable properties.
Nevertheless, phthalate esters are not without drawbacks. Dioctylphthalate has been implicated as a carcinogen causing liver cancer in rats. Their low molecular weights enable them to diffuse out of PVC rapidly and cause “fogging” (cloudy deposits) on glass and other transparent surfaces. Also they are easily extracted by organic solvents, making them unsuitable for use in applications requiring solvent contact.
The prior art in the plasticizer field is typified by the following U.S. patents and Published Applications: U.S. Pat. Nos. 5,777,014; 6,118,012; 6,706,815; 2004/0001948 and 2004/0198909.
U.S. Pat. 5,294,644 discloses surface active lactams which have particularly effective surfactant activity for active organic compounds such as agriculture chemicals and drugs. Many other interesting properties are attributed to such lactams including anti-stat, anti-block and lubricant properties. The particular utility for these lactams was its ability to form stable emulsion concentrates of water insoluble agricultural chemicals.
Accordingly, it is an object of this invention to provide long term plastification to PVC so as to impart flexibility, softness, extensibility and/or lower melting temperatures to PVC compositions.
Another object herein is to provide such plasticized PVC compositions for such applications as films, siding, sheets, pipe and tubing as well as calendered sheets, plastisols, foams and dispersions.